Infusion pump, treatment fluid bag therefor, and method for the use thereof

ABSTRACT

An infusion pump for infusing a medical treatment fluid intravenously to a patient includes a collapsible treatment fluid bag juxtaposed with an inflatable drive fluid bladder confined between a pair of opposing containment members which cause the bladder to impinge against the bag as the bladder is inflated. A drive fluid pump controllably inflates the bladder, thereby displacing treatment fluid from the bag into an outlet tube affixed thereto which conveys the treatment fluid to the patient where it is received intravenously. The treatment fluid flow rate through the tube is controlled by increasing or decreasing the drive fluid pump output and consequently the pressure in the bladder in response to a pressure sensor in fluid communication with the bladder. Alternatively, the treatment fluid flow rate is adjusted by opening or closing the outlet tube by means of an occluder or restrictor positioned along the tube.

FIELD OF THE INVENTION

The present invention relates generally to apparatus and methods for theintravenous infusion of medical treatment fluid to a patient. Moreparticularly, the present invention pertains to a pump for theintravenous infusion of medical treatment fluid to a patient, andmethods for the use of such pump. In a particular aspect, the presentinvention relates to an intravenous infusion pump operated by inflationof a bladder which impinges against a flexible treatment fluidreservoir.

BACKGROUND OF THE INVENTION

Intravenous administration sets which are useful for infusing medicaltreatment fluids to a patient are well known and widely used. In themost simple configuration, the intravenous fluid administration setincludes a fluid source, an intravenous line connecting the fluid sourceto the patient, and a device operatively associated with the intravenousline to influence the rate of fluid flow to the patient. Flow ratecontrol devices are characterized as either pumps or controllers.Controllers rely on gravity for the flow of treatment fluid through thesystem, while pumps exert an electromechanical force on the fluid toestablish a fluid flow.

Pumps are often preferred because they can deliver higher pressures andcan accurately deliver a wide range of flow rates. However, pumps havesome inherent disadvantages which render them less than ideal, e.g.,cost, complexity, size, and (lack of) mobility. There is, therefore, aneed for pumps which are relatively small and simple to operate, yetwhich are relatively accurate and reliable (and which preferably utilizea minimum number of components in the fluid containment and delivery setthereof). The ability to produce such a pump which is portable and whichis relatively inexpensive to manufacture would be beneficial in thefield of medical treatment fluid delivery, especially in the home caresetting.

SUMMARY OF THE INVENTION

In one aspect, the present invention comprises an infusion pump forinfusing a medical treatment fluid intravenously to a patient. Inanother aspect, the present invention comprises a method for infusingintravenous fluid to a patient. In yet another aspect, the presentinvention comprises novel treatment fluid bags useful with the inventionpump.

The invention infusion pump comprises a collapsible treatment fluid bagand an inflatable drive fluid bladder juxtaposed therewith. Theinvention infusion pump further comprises a control assembly tocontrollably inflate the bladder, so as to establish (and maintain) adesired pressure in the treatment fluid bag. The treatment fluid bag andbladder are positioned between opposing containment members which causethe bladder to impinge against the bag as the bladder is inflated.

The treatment fluid bag has an outlet tube affixed thereto which enablestreatment fluid to exit the bag as it is being collapsibly compressed byimpingement of the bladder thereagainst. The outlet tube is in fluidcommunication with the patient to convey the treatment fluid to thepatient where it is received intravenously. The effluent flow ratethrough said outlet tube can readily be determined once a set pressureis established in the fluid treatment bag, e.g., by using an outlet tubehaving a predetermined fixed cross-sectional area which is defined bythe inside diameter of the tube, or alternatively by a fixed flowrestriction positioned along the length of tubing.

The infusion pump of the present invention has numerous advantages overprior art pumps, combining many desirable features such as accuracy, lowcost, low power requirements, ease of operation, and the like, into alight-weight, self-contained, relatively small unit. The invention unitcan be readily reconfigured in a variety of ways to adapt to therequirements of different therapies. For example, a wide range of flowprofiles, rates of fluid delivery, volumes of fluid delivered, and thelike, can be accomodated by the invention infusion pump. The inventionunit employs a treatment fluid bag which can be readily filled, withtreatment fluid administered to the patient by way of a simple, reliabledelivery system.

The invention pump and delivery system employing same have certaininherent safety features. For example, the pressure under which thetreatment fluid is delivered to the patient is limited by the design ofthe pump, in contrast to prior art pumps which may expose the patient tothe possibility of pressures as high as 35 psi (or higher) in the eventof malfunction. In addition, the possibility of free flow of treatmentfluid from the treatment fluid bag is not possible with the inventionpump, whereas prior art pumps may subject the patient to the possibilityof exposure to a free flow of treatment fluid in the event ofmalfunction.

The novel features of this invention, as well as the invention itself,both as to its structure and its operation, will be further understoodfrom the accompanying drawings, taken in conjunction with theaccompanying description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one embodiment of the infusion pump ofthe present invention.

FIG. 2 is a cross-sectional view as seen along line 2--2 in FIG. 1,wherein the cover plate of the infusion pump has been removed.

FIG. 3 is a cross-sectional view of the cover plate for the inventioninfusion pump, as seen along line 3--3 in FIG. 1.

FIG. 4 is a schematic of the control assembly for the infusion pumpshown in FIG. 2.

FIG. 5 is a broken cross-sectional view corresponding to the view ofFIG. 3 showing another embodiment of the infusion pump of the presentinvention.

FIG. 6 is a schematic of the control assembly for the infusion pumpshown in FIG. 5.

FIG. 7 is a perspective view of another embodiment of the infusion pumpof the present invention.

FIG. 8 is a schematic of a treatment fluid bag of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the present invention, there is provided a pump forinfusing intravenous treatment fluid to a patient. The inventioninfusion pump comprises:

a collapsible treatment fluid bag;

an inflatable bladder juxtaposed with said treatment fluid bag;

means to vent said bladder;

means for impinging said bladder against said treatment fluid bag assaid bladder inflated;

means for controllably inflating said bladder to collapse said treatmentfluid bag and expel treatment fluid therefrom; and

an outlet tube in fluid communication with said treatment fluid bag andsaid patient.

In accordance with another embodiment of the present invention, there isprovided a collapsible fluid treatment bag comprising:

an attached extension set;

activator means capable of interacting with the means for controllablyinflating said bladder so as to enable the means for controllablyinflating said bladder to operate; wherein said means for controllablyinflating said bladder is disabled in the absence of said activatormeans; and

a port for introducing fluid into said treatment bag.

In accordance with yet another embodiment of the present invention,there is provided a method for infusing intravenous treatment fluid to apatient comprising:

positioning an inflatable bladder in juxtaposition with afluid-containing collapsible treatment fluid bag within a confinedcontainment volume formed by first and second opposing containmentmembers;

controllably inflating said bladder, thereby impinging said bladderagainst said treatment fluid bag;

collapsing said treatment fluid bag to expel treatment fluid therefrominto an outlet tube in fluid communication with said treatment fluidbag, wherein treatment fluid is controllably expelled from saidtreatment fluid bag at a predetermined rate; and

displacing said treatment fluid through said outlet tube to the patient.

The collapsible treatment fluid bag contemplated for use in the practiceof the present invention can be made of materials commonly employed toproduce flexible bags of the type conventionally used to retain medicaltreatment fluids for intravenous infusion. Examples of such materialsinclude polyvinyl chloride (PVC), polyolefins (e.g., polypropylene),polyurethanes, and the like. The treatment fluid bag is preferablyfilled before placement in the containment means which enables theinflated bladder to impinge the treatment fluid bag. Alternatively,treatment fluid bag can be placed in the containment means, then filledwith treatment fluid. The treatment fluid bag can be filled to anysuitable volumetric capacity; typically between about 100 ml and 5000ml.

Treatment fluid bags contemplated for use in the practice of the presentinvention can be viewed as modified versions of conventionally availabletreatment fluid bags. One such modification is the presence (oninvention treatment fluid bags) of activator means capable ofinteracting with the control assembly of the abovedescribed infusionpump, so as to enable the control assembly of said pump to operate;wherein the control assembly is disabled in the absence of the activatormeans. The presence of the activator means ensures that the inventionpump is operable for the delivery of treatment fluid to the patient onlywhen a treatment fluid bag containing the desired treatment fluid isinserted into the containment means of the pump. Thus, only the desiredtreatment fluid is delivered to the patient, and such treatment fluid isprovided at an appropriate target flow rate. At the same time, deliveryof treatment fluids not contemplated for use with the particularconfiguration (i.e., flow rate, quantity of treatment fluid, etc) of theinvention pump is prevented.

Examples of activator means useful in the practice of the presentinvention include mechanical means (e.g., lock and key operation,switch, bag configuration (so that only the appropriate bag size andconfiguration will fit in the containment means), and the like),magnetic means (e.g., positioning a magnet in the containment means anda piece of ferrite in the fluid treatment bag, so that positioning ofthe treatment fluid bag in the containment means enables the controlcircuit), electrical contact (so that appropriate positioning of thefluid treatment bag in the containment means completes a circuitrequired to enable the control circuit), optical coupling (so that thepresence of the treatment fluid bag is required for the optical circuitto be completed), and the like.

In addition to the activator means, the extension set of the inventiontreatment fluid bag optionally further comprises a built-in flowrestrictor; fitment for attaching the treatment fluid bag to a needle orto a patient's catheter site; clamp to stop the flow of the treatmentfluid before, during or after delivery of the treatment fluid to thepatient; a filter in the tubing line; and the like.

Inflatable bladder(s) contemplated for use in the practice of thepresent invention is formed from an expandable material which incurssubstantially no strain energy as it is expanded to a size whichcorresponds to substantially the entire volume of the containment meansin which the treatment fluid bag and bladder are positioned. Exemplarymaterials from which bladders useful in the practice of the inventioncan be prepared include polymeric materials, rubber-filled orpolymer-filled cloth, and the like. Accordion-type bladders, prefoldedor pre-creased bladders, or any of a variety of other collapsibleconfigurations are suitable.

It is also desirable to be able to controllably vent the bladder, so asto reduce the flow rate of treatment fluid from the bladder, terminateflow of treatment fluid, allow disassembly and servicing of theinvention pump, and the like. Such venting can be accomplished in avariety of ways. For example, a vent having a pinch clamp thereon can beprovided on the bladder. Alternatively, the drive fluid pump can be areversible pump, so that the pump can be employed to remove drive fluidfrom the bladder. As another alternative, the latch means used to securethe base to the cover of the invention pump assembly can serve multiplepurposes, i.e., latching the pump assembly, activating the unitelectronically, and closing off the vent means for the bladder.

The means for impinging the bladder against the treatment fluid bag asthe bladder is inflated can be provided in a variety of ways. Forexample, such means can be provided by containment members, which maycomprise a variety of structures. Optionally, one or more of thecontainment members will include a member complementary to the activatormeans of the treatment fluid bag, so that the juxtaposition ofcontainment member(s) and treatment fluid bag will cooperate to enablethe means for controllably inflating the bladder to operate (when themeans for controllably inflating said bladder is disabled in the absenceof said activator means).

In one embodiment a first containment member is a rigid platen having aplanar surface and a second containment member is a rigid base having areceptacle formed therein to retain the drive fluid bladder and toreceive the treatment fluid bag. The base and platen are removablyengageable to fully enclose the bag and bladder. Guide members arepreferably provided on the platen and base to enable slidable engagementthereof after placement of fluid treatment bag in the base. Preferably,a latch is further provided to securely lock engagement of the platenand base in place.

In another embodiment, a first containment member is a rigid platenhaving a receptacle formed therein to retain the drive fluid bladder andto receive the treatment fluid bag, and a second containment member is arigid base having a planar surface. As with the previously describedembodiment, the base and platen are removably engageable to fullyenclose the bag and bladder. Guide members are preferably provided onthe platen and base to enable slidable engagement thereof afterplacement of a fluid treatment bag in the platen. Preferably, a latch isfurther provided to securely lock engagement of the platen and base inplace.

In yet another embodiment, a first containment member is a rigid platenhaving a planar surface. A second containment member is a flexible, yetsubstantially inelastic sheet, loosely attached to the platen atopposite sides to form a sling. The bladder is positioned in the slingand the infusion pump is assembled by sliding a treatment fluid bag intothe sling in abutment with the bladder, and optionally attaching theoutlet tube to the bag. In a preferred embodiment, the treatment fluidbag employed will include its own pre-attached extension set, optionallycontaining its own flow restrictor.

Containment members contemplated for use in the practice of the presentinvention can be formed from high-strength materials such as rigidplastics, flexible plastics, semi-rigid plastics, die-cast aluminum, andthe like.

Means for controllably inflating the drive fluid bladder contemplatedfor use in the practice of the present invention are provided by acontrol assembly, which comprises a pressure sensor, in operativecommunication with a suitable control circuit, which is, in turn, inoperative communication with a drive fluid pump. Optionally, the controlassembly may contain a display for operator interface. Optionally,control assembly may also include a member complementary to theactivator means of the treatment fluid bag, so that the juxtaposition ofthe control assembly and treatment fluid bag will cooperate to enablethe control assembly to operate (when the control assembly is disabledin the absence of said activator means).

The control assembly can be provided as an integral part of the pump ofthe invention, or can be provided as a separate module, so long ascommunication means is provided to introduce drive fluid from the drivefluid pump into the drive fluid bladder. Housing can be provided for thecontrol assembly to be positioned internal to such housing, as shown,for example, in FIG. 1. Such control assembly housing can further beintegral with the base and/or cover of the pump assembly. The pumpassembly can further comprise an input station comprising a plurality oftouch keys for entering operational commands to the control assembly.Alternatively, separate housing can be provided for the control assemblywhich is then employed as a separate module positioned in convenientproximity to the containment means in which the treatment fluid bag anddrive fluid bladder are positioned.

Control circuits contemplated for use in the practice of the presentinvention provide means to establish a set point pressure, means forcomparing the set point pressure to the actual pressure in the bladder(e.g., a comparator), and means capable of driving the drive fluid pumpmotor (e.g., a switch to turn on the motor). Such a control circuit canoptionally contain an op-amp to amplify the pressure signal from thepressure sensor. Alternatively, a pressure switch can be employed tocontrol the operation of the drive fluid pump.

Drive fluid pumps contemplated for use in the practice of the presentinvention are readily available and are well known in the art ofautomatic blood pressure monitors. Any drive means capable of producinga positive displacement of drive fluid on each stroke can be employed.Examples include an eccentric cam driving a diaphragm, a bellows, andthe like; various solenoid configurations driving a diaphragm, abellows, and the like; a stepper motor with an axial lead screw shaftdriving a diaphragm, a bellows, and the like;, a rotary vein-type pumpdriven by a DC motor, a stepper motor, and the like; and so on.

Conventional flexible plastic medical tubing having a predeterminedfixed inner diameter is suitable for use as the outlet tube employed inthe practice of the present invention. A flow restrictor may optionallybe positioned along the length of such tubing, intervening in thetreatment fluid flowpath of the outlet tube. The presence of a flowrestrictor serves to further narrow the inner diameter of the outlettube to a reduced fixed inner diameter.

The treatment fluid flow rate through the outlet tube can be controlledin a variety of ways. According to one such control method, thetreatment fluid flow rate is adjusted either up or down bycorrespondingly increasing or decreasing the drive fluid pump output andconsequently the pressure in the bladder. For this purpose a pressuresensor is provided in fluid communication with the drive fluid bladder.The pressure sensor supplies pressure measurements to a control circuitregulating the pump output. Both the pressure sensor and control circuitare preferably retained within a control housing integral with one orboth containment members. A command input station may also be providedon the housing in communication with the control circuit to enable anoperator to program a specific sequence of operating parameters into thecontrol circuit.

According to an alternate control method, the treatment fluid flow ratecan be adjusted by increasing or decreasing the opening of the outlettube by means of an occluder or restrictor positioned therealong. Forexample, the fluid flow rate can be adjusted to one of two levels, i.e.,either full flow or no flow, by correspondingly opening or closing theoutlet tube by means of an occluder. The occluder is preferably a clampexternal to the outlet tube which operates by pinching off the flexibleoutlet tube to close it and releasing the tube to open it. For thispurpose a control circuit is provided to dictate the position of theoccluder. An input station in communication with the control circuit mayalso be provided to enable the operator to program a specific sequenceof occluder operation as a function of time.

As those of skill in the art recognize, combination(s) of theabove-described pressure control/flow control methodology can also beemployed. For example, a flow profile defined by the drive fluid pumpoutput can be further modified by the operation of an occluder orrestrictor in combination therewith.

Referring now to FIG. 1, a first embodiment of an infusion pump of thepresent invention is shown and generally designated 10. Infusion pump 10is housed within a pair of containment members, the lower containmentmember 12 being the base and the upper containment member 14 being acover plate termed a platen. Retained within receptacle 16 formed bybase 12 is a prefilled collapsible treatment fluid bag 18. Extendingfrom bag 18 is a flexible outlet tube 20 which exits receptacle 16 viaopening 22 in base 12. Tube 20 extends to a patient in whom thetreatment fluid is to be intravenously infused. A site adaptor fitting24 is provided at the end of tube 20 which enables communication betweentube 20 and a Vein of the patient.

Tube 20 is a conventional flexible plastic medical tubing having apredetermined fixed inner diameter. A flow restrictor 26 may optionallybe positioned along tube 20 which intervenes in the treatment fluidflowpath of tube 20 to further narrow the inner diameter of tube 20 asoriginally manufactured to a reduced fixed inner diameter.

As shown in FIG. 1, housing 28 can be provided for a control assemblywhich, in this embodiment, is positioned internal to housing 28, asdescribed hereafter. Control assembly housing 28, in this embodiment, isintegral with base 12 and has an input station 30 on its face comprisinga plurality of touch keys 32 for entering operational commands to thecontrol assembly.

Positioned on cover plate 14 is a latch 34 extending from a latchopening 36 in plate 14. Latch 34 is provided for locking cover plate 14in place upon engagement with base 12. Drive fluid vent 38 (formed inbase 12) is preferably positioned in alignment with latch opening 36 andlatch 34 when cover plate 14 engages base 12. Vent 38 enables dischargeof drive fluid from a drive fluid bladder, which is retained withinreceptacle 16 described hereafter with reference to FIG. 2, when latch34 is in the unlocked position as shown. Once latch 34 is slid into thelocked position over vent 38, discharge of drive fluid is blocked.

In accordance with this embodiment, infusion pump 10 is furtherdescribed with reference to FIG. 2 which shows the pump componentsinternal to control assembly housing 28 and base 12 having cover plate14 removed therefrom. Collapsible fluid treatment bag 18 is positionedto easily fit within receptacle 16 with outlet tube 20 extendingtherefrom via opening 22. Positioned beneath bag 18 and juxtaposedtherewith is inflatable bladder 68 (shown in a deflated state).Operation of bladder 68 is under the control of a control assemblygenerally designated 70 which is contained within housing 28.

Assembly 70 comprises a drive fluid pump 72 in fluid communication withbladder 68 via drive fluid inlet tube 74. Bladder 68 has a drive fluidoutlet tube 75 in fluid communication with a drive fluid outlet port 76.Pump 72 receives drive fluid from an external source, such as theambient atmosphere, via drive fluid feed port 77. A pressure sensor tube78 is in fluid communication with drive fluid inlet tube 74 to providefluid communication between pressure sensor so and bladder 68. Pressuresensor so may be a pressure transducer having a linear output or apressure switch having an on/off nonlinear output. Sensors suitable forthis purpose include solid state sensors, mechanical sensors, capacitivesensors, reluctance-type sensors, and the like. Operational commands forassembly 70 are generated in a control circuit, e.g., a microprocessor,integral with electronics board 82. The control circuit may bepreprogrammed or alternatively reprogrammable by means of input station30 shown in FIG. 1.

Electronics board 82 electrically communicates with pump 72 and sensorso via lines 84 and 86, respectively. The components of assembly 70 canall be powered from a single electrical power source 92 whichdistributes power via lines 94a, 94b. Power source 92 may be an internalbattery as shown here which is either replaceable, rechargeable, orsimply disposable along with the entire infusion pump 10 upon use.Alternatively, the power source can be external to assembly 70 such ascommon household current.

Base 12 and cover plate 14 can be fixably engaged in a variety of ways,such as, for example, by a combination of pivot means and latching means(wherein pivot means and latching means can be positioned on the front,side, or back of the base and/or cover plate, wherein the pivot meansand latching means are preferably positioned on opposing sides of thebase and/or cover plate), by slidable engagement of base and cover platein combination with pivot means, by use of a latch which is actuated bythe bladder as the bladder is inflated, and the like. As shown in FIG. 3(which shows cover plate 14), a presently preferred means of suchattachment comprises providing rail segments 96 and latch coupling 97 onthe outside edge of base 12. The rail segments and latch coupling enablefixable engagement of base 12 and cover plate 14. Rail segments 98 areprovided along the bottom of inside edge 100 of cover plate 14. Railsegments 98 are positioned to align beneath rail segments 96 of base 12when cover 14 is slid over receptacle 16 of base 12. Latch 34 ispositioned within latch opening 36 to lock rail segments 96, 98 in placerelative to each other when latch 34 is hooked through slot 102 and overlatch coupling 97 on base 12. When latch 34 is in the locked position,it plugs drive fluid vent 38 of cover 14 which is in alignment with port76 of base 12 in fluid communication with bladder 68.

FIG. 5 shows an alternate embodiment of a control assembly generallydesignated 70a wherein occluder 104 is provided on tube 20 immediatelyinside opening 22 to enable closure of tube 20 and stoppage of treatmentfluid flow therethrough as desired. An occluder motor 106 (e.g., asolenoid, a latching solenoid, a step-motor actuator, various mechanismsin cooperation with a motor, such as an over-the-counter mechanism,eccentric cam actuator, and the like) adjacent occluder 104 and incommunication with power source 92 and suitable control circuit, e.g.,microprocessor, via lines 108 and 110, respectively, activates occluder104 on command from the control circuit. A clock is further providedintegral with electronics board 82 to provide control input to thecontrol circuit. It is to be understood that although control assemblies70 and 70a have been described above with reference to infusion pump 10,similar control assemblies can be provided with infusion pump 40 toperform the same function.

FIG. 7 shows an alternate embodiment of the infusion pump of the presentinvention generally designated 40. Infusion pump 40, like infusion pump10, has a pair of containment members including a rigid platen 42 as theupper containment member. The lower containment member 44, however, is aflexible, yet substantially inelastic and unstretchable sling preferablyformed from a high-strength mesh or cloth fabric, such as a nylon mesh.Sling 44 has a rectangular shape having two opposing sides 46a, 46bfastened to the bottom 48 of platen 42 such that sling 44 hangs looselytherefrom with openings 50a, 50b at the front and back of sling 44,respectively.

An inflatable drive fluid bladder 52 is retained in sling 44. Acollapsible treatment fluid bag 54 is removeably positioned in sling 44juxtaposed with bladder 52. Positioning of bag 54 in sling 44 isaccomplished by sliding prefilled bag 54 into sling 44 through eitheropening 50a or 50b, while the bladder 52 is retained therein. Extendingfrom bag 54 to the patient is treatment fluid outlet tube 56 having asite adaptor fitting (not shown) positioned at the end of tube 56opposite bag 54 which enables intravenous infusion of the treatmentfluid into the patient.

Tube 56 is a conventional flexible plastic medical tubing having apredetermined fixed inner diameter. A flow restrictor 58 may optionallybe positioned along tube 56. Platen 42 is formed from a high-strengthrigid material such as a rigid plastic. Collapsible bag 54 is a flexibleplastic bag of the type conventionally used to retain medical treatmentfluids for intravenous infusion. Bag 54 typically has a volumetriccapacity larger than that of bag 18 of the first embodiment and ispreferably between about 1000 ml and 5000 ml.

Inflatable drive fluid bladder 52 has a drive fluid tube 60 extendingtherefrom, through opening 50b, and into control assembly housing 62where tube 60 connects to a drive fluid pump, thereby providing fluidcommunication between bladder 52 and the drive fluid pump described withreference to FIG. 2. Control assembly housing 62 is integral with platen42 and has an input station 64 on its face comprising a plurality oftouch keys 66 for entering operational commands to the control assemblycontained within housing 62.

As used herein, the term "portable" pumps refers to pumps which aresmall enough (and lightweight enough) to carry around without the needfor special transport means, operate on their own power source (withoutthe need for an independent source of power), are rugged enough towithstand the impact of constant and/or frequent movement, and the like.

An exemplary treatment fluid bag of the invention is shown in FIG. 8wherein 12 refers to the base in which the treatment fluid bag isretained, 16 refers to the receptacle formed by base 12, 18 refers tothe treatment fluid bag, 20 refers to flexible outlet tube, 22 refers tothe opening in base 12 wherethrough the flexible outlet tube passes, 26refers to the optional flow restrictor, 24 refers to a site adaptorfitting, 25 refers to the fill port; 31 refers to an air vent; and 27and 29 refer to means to incorporate activator means into thecontainment means and treatment fluid bag of the invention,respectively.

OPERATION

Operation of pump 10 is now described with reference to FIGS. 1-5, itbeing further understood that the present operational descriptionapplies similarly to pump 40, as well as to other variations. Infusionof treatment fluid is performed in one instance by placing a prefilledtreatment fluid bag 18 in receptacle 16 atop bladder 68 after cover 14is removed from base 12. Outlet tube 20 is fed through opening 22.

Cover 14 is slid back onto base 12 such that rail segments 96 engagerail segments 98. The tight fit of bag 18 in receptacle 16 impinges bag18 against bladder 68 as cover 14 is being positioned driving anyresidual drive fluid retained in bladder 68 out into the surroundingatmosphere via tube 74, port 76, and vent 38. The preferred drive fluidis ambient air. Latch 34 is then slid shut to lock cover 14 in place andseal off vent 38 from the atmosphere. Closing of latch 34 can cooperatewith a switch (not shown) to activate drive fluid pump 72. In analternate embodiment drive fluid pump 72 can be activated by theoperator through a command to input station 30 which communicates withthe control circuit of electronics board 82.

When drive fluid pump 72 is activated, it draws air through drive fluidfeed port 77 and feeds it under pressure to bladder 68 via tube 74. Thepressurized air inflates bladder 68 within the confined receptacle 16impinging both bladder 68 and bag 18 against the inner surfaces of base12 and cover 14. Once the treatment fluid bag is pressurized, thecontents thereof can be purged of air (e.g,, by opening the clamp andletting air out of the bag, then closing the clamp) and placed incommunication with a desired vein of a patient using site adaptor 24 atthe end of tube 22.

Bag 18 collapses at a rate proportional to the rate at which treatmentfluid is expelled from the bag, thereby giving bladder 68 increasingamounts of space in which to expand. Bladder 68 can be inflated until itfills the entire volume of confined receptacle 16, thereby completelycollapsing bag 18 and expelling treatment fluid therefrom, therebydelivering treatment fluid to the patient.

In the embodiment of FIG. 2, the flow rate of treatment fluid to thepatient is governed by the fixed cross-sectional area of outlet tube 20and the pumping pressure of drive fluid pump 72. A cross-sectional areaof the tube can be selected other than its area of manufacture by fixingflow restrictor 58 on tube 20 to reduce its cross-sectional area.Variable flow rate adjustment is achieved by means of control assembly70 shown in FIG. 2 and further shown schematically in FIG. 4 which actsas a feedback circuit. Whenever pressure sensor 80 measures too low apressure, it is detected by the control circuit which sends a signal todrive fluid pump 72 to increase its output up to the desired level. Ifthe measured pressure is too high, the control circuit conversely sendsa signal to drive fluid pump 72 to decrease its output accordingly.

In the embodiment of FIG. 5 (also shown schematically in FIG. 6),treatment fluid flow rate is regulated by fully opening or closing tube20 in correspondence with occluder 104 Operation of occluder 104 isgoverned by commands from the control circuit integral with electronicsboard 82 which further utilizes the clock also integral with electronicsboard 82 to determine tube 20 opening and closing times. In eithercontrol assembly embodiment, the operator can program additional controlcommands into the control circuit via input station 30 if desired.

The materials for construction of pumps 10 and 40 are generally andpreferably selected to be both inexpensive and lightweight. This enablesthe pump of the present invention to be portable and, if desired,disposable after each of one or several uses.

While the particular infusion pumps as herein shown and disclosed indetail are fully capable of obtaining the objects and providing theadvantages herein before stated, the disclosure is to be understood asmerely illustrative of the presently preferred embodiments of theinvention.

We claim:
 1. A pump for infusing intravenous treatment fluid to apatient, said infusion pump comprising:a collapsible treatment fluidbag; an inflatable bladder juxtaposed with said treatment fluid bag;means .[.to vent.]. .Iadd.for venting .Iaddend.said bladder; means forimpinging said bladder against said treatment fluid bag as said bladderis inflated; means for electronically controlling the pressure of saidbladder so as to collapse said treatment fluid bag and controllablyexpel treatment fluid therefrom; and an outlet tube in fluidcommunication with said treatment fluid bag and said patient.
 2. A pumpaccording to claim 1 wherein said outlet tube has a predetermined andsubstantially fixed cross-sectional area.
 3. A pump according to claim 1further comprising an occluder for selectively blocking treatment fluidflow across said outlet tube.
 4. A pump according to claim 1 whereinsaid means for electronically controlling the pressure of said bladdercomprises a pressure .[.sensing means.]. .Iadd.sensor.Iaddend., inoperative communication with a suitable electronic control circuit,which is, in turn, in operative communication with a drive fluid pump.5. A pump according to claim 4 further comprising an internal powersource for said means for electronically controlling the pressure ofsaid bladder.
 6. A pump according to claim 1 wherein said means forimpinging comprises first and second opposing containment membersconfining said juxtaposed bladder and fluid bag.
 7. A pump according toclaim 6 wherein said first containment member has a rigid planar surfaceand said second containment member is a flexible sheet engaging saidfirst containment member.
 8. A pump according to claim 6 wherein saidfirst containment member is a rigid base and said second containmentmember is a rigid cover plate removably engageable with said base toenclose said bag and bladder therein.
 9. A portable pump for infusingintravenous treatment fluid to a patient, said infusion pumpcomprising:a collapsible treatment fluid bag; .Iadd.a pressure sensor;.Iaddend. an inflatable bladder juxtaposed with said treatment fluidbag, wherein said bladder is in fluid communication with .[.a.]..Iadd.said .Iaddend.pressure sensor; means for venting said bladder; acontainment means for impinging said bladder against said treatmentfluid bag as said bladder is inflated, said containment means comprisingfirst and second opposing containment members confining said juxtaposedbladder and fluid bag; an electronic control assembly comprising a drivefluid pump in fluid communication with said bladder for inflating saidbladder to collapse said treatment fluid bag and expel treatment fluidtherefrom.[.;.]..Iadd., .Iaddend.wherein said drive fluid pump is alsoin .[.fluid.]. .Iadd.operative .Iaddend.communication with an electroniccontrol circuit, which is, in turn, in .[.fluid.]. .Iadd.operative.Iaddend.communication with said pressure sensor; and an outlet tube influid communication with said treatment fluid bag and said patient. 10.A portable pump according to claim 9 wherein said outlet tube has apredetermined and substantially fixed cross-sectional area.
 11. Aportable pump according to claim 9 further comprising an occluder forselectively blocking treatment fluid flow across said outlet tube.
 12. Aportable pump according to claim 11 further comprising a control circuitin communication with said occluder for directing opening and closing ofsaid occluder as a function of time.